[1] Univ Pittsburgh, Crit Care Med, Pittsburgh, PA USA
[2] Carnegie Mellon Univ, Engn & Publ Policy, Pittsburgh, PA USA
[3] Harborview Med Ctr, Pulm Crit Care & Sleep Med, Seattle, WA USA
[4] Univ Toronto, Dept Surg, Toronto, ON, Canada
[5] Univ Penn, Philadelphia, PA USA
[6] Univ Alberta, Crit Care Med, Edmonton, AB, Canada
[7] Univ Calif San Francisco, Div Hosp Med, San Francisco, CA USA
[8] Univ Pittsburgh, Dept Crit Care Med, Med Ctr, Pittsburgh, PA USA